This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application IMAGE FORMING APPARATUS HAVING STRUCTURE FOR PREVENTING NOISE AND VIBRATION OF DEVELOPING DEVICE filed with the Korean Industrial Property Office on May 9, 2001 and there duly assigned Serial No. 25078/2001.
1. Technical Field
The present invention relates to an electrophotographic image forming apparatus, such as a laser printer or a photo-copying machine. More particularly, the invention relates to a structure of an electrophotographic image forming apparatus capable of preventing noise and vibration generated from a developing device during the printing process.
2. Related Art
A laser printer, which is an image forming apparatus, uses an electrophotographic method to form an electrostatic latent image by projecting a laser beam onto a charged photosensitive medium, develops the electrostatic latent image as a visible image by use of toner particles, and transfers and settles the electrostatic latent image on a printing paper.
The laser printer comprises a paper-distributing unit for transferring paper from a stack of paper disposed in a tray to a paper-transferring path, a developing device which forms a toner image based on a printing signal on a photosensitive drum by means of an electrophotographic process, and which transfer the toner image from the paper distributing unit to the transferred paper, and a settling unit for settling the toner image transferred to the paper.
In prior developing devices, when the amount of toner supplied to the photosensitive drum from the supplying roller through the developing roller is small (in other words, when an image having little data is printed, or when the toner in the toner accommodating chamber is almost used), the toner insufficiently covers the surfaces of the supplying roller, the developing roller, the charging roller, the transferring roller and the photosensitive drum. Accordingly, the surface of each roller and of the photosensitive drum directly contact each other. Therefore, abrasion of the rollers, as well as noise and vibration, can occur due to friction between the rollers and the photosensitive drum which, in turn, is due to their rotating in direct contact with each other. In addition, a resonance is generated since a frequency, which is generated by the noise and the vibration caused by the friction between the rollers and the photosensitive drum, is overlapped with a natural frequency of the developing roller and the photosensitive drum. The noise becomes exacerbated due to the resonance, and the printing of the image cannot be performed well because of the vibration of the entire image forming apparatus.
The present invention has been developed to overcome the above-mentioned problems of the related art.
Accordingly, it is an object of the present invention to provide an image forming apparatus having a structure which prevents noise and vibration from being generated in a developing device, even when the rollers and the photosensitive drum are rotated in direct surface contact with each other due to an insufficient amount of toner.
The above object is accomplished by providing an image forming apparatus which includes the photosensitive drum, a pivot disposed at the center of the photosensitive drum for rotatably supporting the photosensitive drum, and a mass body disposed on the pivot of the photosensitive drum for changing a frequency of the pivot by changing the center of gravity and the shape of the pivot.
According to the present invention, noise and vibration of the developing device, generated due to friction between rollers and the photosensitive drum, is absorbed by the mass body. Moreover, since the frequency of the pivot is changed, exacerbation of the noise and the vibration can be prevented by a resonance among the noise, the vibration frequency, and the natural frequency of the pivot.
The mass body is disposed at the pivot and at a predetermined distance from an inner circumference of the photosensitive drum. The main body has a form capable of adding a distributed load longitudinally along the pivot, and is positioned toward the area at which noise and vibration of the photosensitive drum are generated.
Preferably, the mass body is made of rubber material, so that the effect of absorbing noise and vibration is increased.